The present invention relates to a windmill structure and more particularly to a windmill used primarily for converting wind energy to mechanical and/or electrical energy.
The wind energy has hardly been utilized effectively nowadays although the same is one of the greatest sources of energy obtainable on the earth. This is due to the fact that it is quite difficult to utilize the wind energy mainly because the wind changes so often both in wind direction and wind velocity. It is apparent that the wind contributes to a mankind as a clean and indefinite energy source if it could be effectively converted to other energies such as an electrical power.
In order to utilize a wind energy as a stable energy source, it is material to provide a windmill power generator device, which converts the wind energy to a mechanical or rotational energy and then to an electrical energy, and a device for storing the thus obtained electrical energy. One of the greatest problems inherent to the windmill power generation is a structure of a windmill, because an output of a windmill varies in a square ratio of the diameter of sails, or wind-engaging blades, of the windmill and in a cubic ratio of the wind velocity. Thus, the windmill which is constructed for the purpose of utilizing a general wind velocity of about 4-5 m/sec. will generate a hundred times of the output in case of the strong wind such as a typhoon or the like. On the other hand, a windmill manufactured solid enough to withstand a strong wind will hardly operate in a general case of the wind velocity of about 4-5 m/sec. or less.
An attenpt has been made to solve these probelms by providing a windmill in which a pitch or twist of the sails is varied in accordance with a wind pressure received by the sails of the windmill. However, such an adjustable pitch type windmill is extraordinarily complex in structure, and therefore it does not meet with economic requirements. Further, it is likely that the sails are broken or damaged due to a "flutter" which is a vibration generated at a change of the wind direction.